1. Field of the Invention
The present invention relates generally to the generation and characterization of neutralizing anti-IFN-α monoclonal antibodies with broad reactivity against various IFN-α subtypes. The invention further relates to the use of such anti-IFN-α antibodies in the diagnosis and treatment of disorders associated with increased expression of IFN-α, in particular, autoimmune disorders such as insulin-dependent diabetes mellitus (IDDM) and systemic lupus erythematosus (SLE).
2. Description of the Related Art
Interferon-α(IFN-α)
Although interferons were initially discovered for their anti-viral activities, subsequent research has unraveled a plethora of regulatory activities associated with these powerful cytokines. Type I interferons form an ancient family of cytokines that includes IFN-α, IFN-β, IFN-δ, IFN-ω and IFN-τ (Roberts et al., J. Interferon Cytokine Res. 18: 805–816 [1998]). They are coded by intronless genes and are widely distributed amongst vertebrates. Whereas IFN-β is coded by a single gene in primates and rodents, more than 10 and 15 different subtypes of IFN-α have been found in mice and man respectively. Other interferons of type I are more restricted, e.g. IFN-δ in the pig, IFN-τ in cattle and sheep, and IFN-ω in cattle and humans. Thus, human type I interferons comprise multiple members of the IFN-α family, and single members of the IFN-β and IFN-ω families. All type I IFNs appear to bind to a single receptor that is comprised of at least two membrane spanning proteins. Type II interferons on the other hand are represented by a single member, IFN-γ, and bind to a distinct receptor.
Although all type I IFNs, including IFN-α, exhibit anti-viral and anti-proliferative activities and thereby help to control viral infections and tumors (Lefevre et al., Biochimie 80: 779–788 [1998]; Horton et al., Cancer Res. 59: 4064–4068 [1999]; Alexenko et al., J. Interferon Cytokine Res. 17: 769–779 [1997]; Gresser, J. Leukoc. Biol. 61: 567–574 [1997]), there are also several autoimmune diseases that are associated with increased expression of IFNα, most notably insulin-dependent diabetes mellitus (IDDM) and systemic lupus erythematosus (SLE).
Type I diabetes, also known as autoimmune diabetes or insulin-dependent diabetes mellitus (IDDM), is an autoimmune disease characterized by the selective destruction of pancreatic β cells by autoreactive T lymphocytes (Bach, Endocr. Rev. 15: 516–542 [1994]; Castano and Eisenbarth, Annu. Rev. Immunol. 8: 647–679 [1990]; Shehadeh and Lafferty, Diabetes Rev. 1: 141–151 [1993]). The pathology of IDDM is very complex involving an interaction between an epigenetic event (possibly a viral infection), the pancreatic β cells and the immune system in a genetically susceptible host. A number of cytokines, including IFN-α and IFN-γ, have been implicated in the pathogenesis of IDDM in humans and in animal models of the disease (Campbell et al., J. Clin. Invest. 87: 739–742 [1991]; Huang et al., Diabetes 44: 658–664 [1995]; Rhodes and Taylor, Diabetologia 27: 601–603 [1984]). For example, pancreatic Ifn-α mRNA expression and the presence of immunoreactive IFN-α in β cells of patients with IDDM have been reported (Foulis et al., Lancet 2: 1423–1427 [1987]; Huang et al., [1995] supra; Somoza et al., J. Immunol. 153: 1360–1377 [1994]). IFN-α expression has been associated with hyperexpression of major histocompatibility complex (MHC) class IA antigens in human islets (Foulis et al., [1987] supra; Somoza et al., [1994] supra). In two rodent models of autoimmune diabetes, the diabetes-prone DP-BB rat and streptozotocin-treated mice, Ifn-α mRNA expression in islets precedes insulitis and diabetes (Huang et al., Immunity 1: 469–478 [1994]). Furthermore, transgenic mice harboring a hybrid human insulin promoter-Ifn-α construct develop hypoinsulinemic diabetes accompanied by insulitis (Stewart et al., Science 260: 1942–1946 [1993]).
It appears that local expression of IFN-α by pancreatic islet cells in response to potential diabetogenic stimuli such as viruses may trigger the insulitic process. Consistent with its role as an initiating agent, IFN-α has been shown to induce intercellular adhesion molecule-1 (ICAM-1) and HLA class IA on endothelial cells from human islets, which may contribute to leukocyte infiltration during insulitis (Chakrabarti et al., J. Immunol. 157: 522–528 [1996]). Furthermore, IFN-α facilitates T cell stimulation by the induction of the co-stimulatory molecules ICAM-1 and B7.2 on antigen-presenting cells in islets (Chakrabarti et al., Diabetes 45: 1336–1343 [1996]). These studies collectively indicate that early IFN-α expression by β cells may be a critical event in the initiation of autoimmune diabetes. Although there are a number of reports implicating IFN-γ in the development of IDDM in rodent models, there is a poor correlation between the expression of this cytokine and human IDDM. Thus, cells expressing IFN-γ can be found in the islets of a subset of human patients selected for significant lymphocytic infiltration into the islets. In a group of patients that were not selected by this criterion there was no obvious association between IFN-γ expression and human IDDM.
Based on the increased level of IFN-α expression in patients with systemic lupus erythematosus (SLE), IFN-α has also been implicated in the pathogenesis of SLE (Ytterberg and Schnitzer, Arthritis Rheum. 25: 401–406 [1982]; Shi et al., Br. J. Dermatol. 117: 155–159 [1987]). It is interesting to note that IFN-α is currently used for the treatment of cancer as well as viral infection such as chronic hepatitis due to hepatitis B or hepatitis C virus infection. Consistent with the observations of increased levels of IFN-α triggering autoimmunity, significant increase in the appearance of autoimmune disorders such as IDDM, SLE and autoimmune thyroiditis has been reported in the patients undergoing IFN-α therapy. For example, prolonged use of IFN-α as an anti-viral therapy has been shown to induce IDDM (Waguri et al., Diabetes Res. Clin. Pract. 23: 33–36 [1994]; Fabris et al., J. Hepatol. 28: 514–517 [1998]) or SLE (Garcia-Porrua et al., Clin. Exp. Rheumatol. 16: 107–108 [1998]). The treatment of coxsackievirus B (CBV) infection with IFN-α therapy is also associated with the induction of IDDM (Chehadeh et al., J. Infect. Dis. 181: 1929–1939 [2000]). Similarly, there are multiple case reports documenting IDDM or SLE in IFN-α treated cancer patients (Ronnblom et al., J. Intern. Med. 227: 207–210 [1990]).
Antibody Therapy
The use of monoclonal antibodies as therapeutics has gained increased acceptance with several monoclonal antibodies (mAbs) either approved for human use or in late stage clinical trials. The first mAb approved by the US Food and Drug Administration (FDA) for the treatment of allograft rejection was anti-CD3 (OKT3) in 1986. Since then the pace of progress in the field of mAbs has been considerably accelerated, particularly from 1994 onwards which led to approval of additional seven mAbs for human treatment. These include ReoPro® for the management of complications of coronary angioplasty in 1994, Zenapax® (anti-CD25) for the prevention of allograft rejection in 1997, Rituxan® (anti-CD20) for the treatment of B cell non-Hodgkin's lymphoma in 1997, Infliximab® (anti-TNF-α) initially for the treatment of Crohn's disease in 1998 and subsequently for the treatment of rheumatoid arthritis in 1999, Simulect® (anti-CD25) for the prevention of allograft rejection in 1998, Synagis® (anti-F protein of respiratory syncitial virus) for the treatment of respiratory infections in 1998, and Herceptin® (anti-HER2/neu) for the treatment of HER2 overexpressing metastatic breast tumors in 1998 (Glennie and Johnson, Immunol. Today 21: 403–410 [2000]).
Anti-IFN-α Antibodies
Disease states that are amenable to intervention with mAbs include all those in which there is a pathological level of a target antigen. For example, an antibody that neutralizes IFN-α present in the sera of patients with SLE, and expressed by the pancreatic islets in IDDM, is a potential candidate for therapeutic intervention in these diseases. It could also be used for therapeutic intervention in other autoimmune diseases with underlying increase in and causative role of IFN-α expression. In both human IDDM (Foulis, et al., Lancet 2: 1423–1427 [1987]; Huang, et al., Diabetes 44: 658–664 [1995]; Somoza, et al., J. Immunol. 153: 1360–1377 [1994]) and human SLE (Hooks, et al., Arthritis & Rheumatism 25: 396–400 [1982]; Kim, et al., Clin. Exp. Immunol. 70: 562–569 [1987]; Lacki, et al., J. Med. 28: 99–107 [1997]; Robak, et al., Archivum Immunologiae et Therapiae Experimentalis 46: 375–380 [1998]; Shiozawa, et al., Arthritis & Rheumatism 35: 417–422 [1992]; von Wussow, et al., Rheumatology International 8: 225–230 [1988]) there appears to be correlation between disease and IFN-α but not with either IFN-β or IFN-γ. Thus, anti-interferon mAb intervention in IDDM or SLE would require specific neutralization of most, if not all, of the IFN-α subtypes, without any significant neutralization of IFN-β or IFN-γ. Leaving the activity of these last two interferons intact may also have an advantage in allowing the retention of significant anti-viral activity.
While a few mAbs that show reactivity with a range of recombinant human IFN-α subtypes have been described, these were found to neutralize only a limited subset of the recombinant IFN-α subtypes analyzed or were not capable of neutralizing the mixture of IFN-α subtypes that are produced by stimulated peripheral blood leukocytes (Tsukui et al., Microbiol. Immunol. 30: 1129–1139 [1986]; Berg, J. Interferon Res. 4: 481–491 [1984]; Meager and Berg, J. Interferon Res. 6: 729–736 [1986]; U.S. Pat. No. 4,902,618; and EP publication No. 0,139,676 B1).
Accordingly, there is a great need for anti-IFN-α antibodies that not only bind to most, preferably all, subtypes of IFN-α but also neutralize such subtypes while do not interfere with the biological function of other interferons.